On Thu, 27 Jul 2017 10:24:46 +0200 Ingo Molnar <[email protected]> wrote:
> > * Masami Hiramatsu <[email protected]> wrote: > > > Since the kernel segment registers are not prepared at the > > entry of irq-entry code, if a kprobe on such code is > > jump-optimized, accessing per-cpu variables may cause > > kernel panic. > > However, if the kprobe is not optimized, it kicks int3 > > exception and set segment registers correctly. > > > > This checks probe-address and if it is in irq-entry code, > > it prohibits optimizing such kprobes. This means we can > > continuously probing such interrupt handlers by kprobes > > but it is not optimized anymore. > > > > Signed-off-by: Masami Hiramatsu <[email protected]> > > Reported-by: Francis Deslauriers <[email protected]> > > Tested-by: Francis Deslauriers <[email protected]> > > --- > > Changes in v4: > > - Fix to use CONFIG_OPTPROBES instead of CONFIG_KPROBES. > > --- > > arch/x86/kernel/kprobes/opt.c | 9 ++++++--- > > include/asm-generic/vmlinux.lds.h | 6 ++++-- > > include/linux/interrupt.h | 3 ++- > > 3 files changed, 12 insertions(+), 6 deletions(-) > > > > diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c > > index 69ea0bc..c26e7f9 100644 > > --- a/arch/x86/kernel/kprobes/opt.c > > +++ b/arch/x86/kernel/kprobes/opt.c > > @@ -29,6 +29,7 @@ > > #include <linux/kallsyms.h> > > #include <linux/ftrace.h> > > #include <linux/frame.h> > > +#include <linux/interrupt.h> > > > > #include <asm/text-patching.h> > > #include <asm/cacheflush.h> > > @@ -251,10 +252,12 @@ static int can_optimize(unsigned long paddr) > > > > /* > > * Do not optimize in the entry code due to the unstable > > - * stack handling. > > + * stack handling and registers setup. > > */ > > - if ((paddr >= (unsigned long)__entry_text_start) && > > - (paddr < (unsigned long)__entry_text_end)) > > + if (((paddr >= (unsigned long)__entry_text_start) && > > + (paddr < (unsigned long)__entry_text_end)) || > > + ((paddr >= (unsigned long)__irqentry_text_start) && > > + (paddr < (unsigned long)__irqentry_text_end))) > > return 0; > > > > /* Check there is enough space for a relative jump. */ > > diff --git a/include/asm-generic/vmlinux.lds.h > > b/include/asm-generic/vmlinux.lds.h > > index da0be9a..3092a1f 100644 > > --- a/include/asm-generic/vmlinux.lds.h > > +++ b/include/asm-generic/vmlinux.lds.h > > @@ -483,7 +483,8 @@ > > *(.entry.text) \ > > VMLINUX_SYMBOL(__entry_text_end) = .; > > > > -#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN) > > +#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN) || > > \ > > + defined(CONFIG_OPTPROBES) > > #define IRQENTRY_TEXT > > \ > > ALIGN_FUNCTION(); \ > > VMLINUX_SYMBOL(__irqentry_text_start) = .; \ > > @@ -493,7 +494,8 @@ > > #define IRQENTRY_TEXT > > #endif > > > > -#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN) > > +#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN) || > > \ > > + defined(CONFIG_OPTPROBES) > > #define SOFTIRQENTRY_TEXT \ > > ALIGN_FUNCTION(); \ > > VMLINUX_SYMBOL(__softirqentry_text_start) = .; \ > > diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h > > index a2fdddd..f95b046 100644 > > --- a/include/linux/interrupt.h > > +++ b/include/linux/interrupt.h > > @@ -726,7 +726,8 @@ extern int early_irq_init(void); > > extern int arch_probe_nr_irqs(void); > > extern int arch_early_irq_init(void); > > > > -#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN) > > +#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN) || \ > > + defined(CONFIG_OPTPROBES) > > Please split the generic changes to asm-generic/vmlinux.lds.h and interrupt.h > into > a separate patch, with its own changelog, because this is not a kprobes/x86 > only > patch anymore. OK. BTW, I think it is a good time to make a new (hidden) Kconfig entry for irqentry, like CONFIG_IRQENTRY and above 3 configs select it. What would you think? Thank you, > > Thanks, > > Ingo -- Masami Hiramatsu <[email protected]>
